Example: The half-cell reaction: 2Fe2+ + 3H2O = Fe2O3(s) + 6H+ + 2e

This half-cell reaction can be decomposed into three simpler reactions, only two of which are found in Table 10.1:

A^ o(Fe/Fe2+) = -2x96.5x0.44 = -85 kJ/mole A^(Fe/Fe2O3) = -120x4.184 = 502 kJ/mole A^o(H2O/O2) = -4x96.5 x(-1.23) = 475 kJ/mole

The first and last of these half-cell reactions are numbers 7 and 1, respectively, in Table 10.1. The middle reaction does not involve either aqueous ions or electrons; its free energy change (at 25oC) is obtained from the Ellingham diagram of Fig. 10.3. The free energy change of the desired half-cell reaction is obtained by algebraically combining the above three component reactions:

A^°(Fe2+/Fe2O3) = 3/2 A^°(H2O/O2) + 3/2 A^°(Fe/Fe2O3) - 2 A^°(Fe/Fe2+) = 129 kJ/mole Converting this to the half-cell EMF by use of Eq (10.30) yields:

Problem 10.2 is another example of combining entries in Table 10.1 to obtain the standard electrode potential of a reaction not listed in the table.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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